Great… I’m sure it’s just a coincidence but at almost that exact time I was working with an imp01 in a relatively hostile electrical environment and its power supply may have been glitching quite severely. I’m highly doubtful that this could have such an impact but I thought I ought to 'fess-up anyway.

Initially I put the trouble I was having with http access on that imp down to the electrical issues but soon spotted separate applications that were similarly affected.